Many different applications in the hydrocarbon refining and petrochemical industries employ the use of steam strippers to remove lower boiling compounds from liquid streams containing various boiling range compounds. The introduction of steam into a steam stripped fractionation column is beneficial for the separation of different boiling compounds. However, if too much steam is added for the amount of heat available in the column, steam will condense on the stripper trays where water builds up and eventually floods the stripper, causing major operational upsets. The presence of liquid water also leads to increased corrosion of the trays and walls of the stripper column.
U.S. Pat. No. 6,640,161, which is incorporated herein by reference, describes a computer method for calculating the dew point and providing a warning of operating conditions which may lead to flooding of the column. The total moles of hydrocarbon passing overhead in the steam stripped fractionation column and the total moles of water as steam passing overhead in the steam stripped fractionation column are measured. Using that information, the mole fraction of water as steam passing overhead in the column is continuously calculated. The overhead pressure of the column is measured, and a continuous determination of the partial pressure of water is made by calculating the product of the mole fraction of water as steam passing overhead in the column and the column overhead pressure. In addition, a continuous determination of the dew point temperature of the steam passing overhead in the column is made. The top temperature of the column is measured and provided to the computer wherein the difference between the calculated dew point temperature of the steam passing overhead in the column and the measured top temperature is calculated. As this calculated difference approaches zero, the potential for flooding the column increases. A predetermined value is selected and compared with the calculated difference in order to generate an alarm to alert the operator of unsatisfactory column operation. Once an alarm is detected, the operator may then make the appropriate adjustments to the column in order to avoid flooding the column.
However, U.S. Pat. No. 6,640,161 does not describe the instrumentation and connections among the instruments needed to make the needed measurements. Without the proper instrumentation, the calculation method will not report useful information and flooding conditions can occur. This leads to expensive repairs and lost production.
Therefore, there is a need for instrumentation for, and methods of, calculating water dew point in a steam stripped fractionation column.